To understand the neural basis of behavior we must know how motor circuits are established, maintained, and how these networks can mature and change to produce different behaviors. Central pattern generator (CPG) networks are endogenously active neural networks that produce rhythmic movements such as vertebrate locomotion and breathing, invertebrate flight, and the movements of the crustacean stomach. CPG networks are established and active before adult-like movements appear. It remains unknown what is modified as such networks mature, the circuit connectivity, the neuromodulatory input, and/or the intrinsic membrane properties of the cells. The stomatogastric nervous system of the embryonic and the adult lobster, Homarus americanus, produce different motor patterns. The goal of my proposed research is to determine if changes in the behavior of the maturing stomatogastric nervous system can be attributed to changes in the circuit connectivity, the neuromodulatory environment or both.